A series of studies will compare memory processes in normal and mildly and moderately retarded persons of the same chronological age. The purpose of the research is to identify and analyze deficiencies in memory and memory related processes. The two initial studies will focus on primary memory, comparing normal and retarded groups on a Brown-Peterson short-term memory task and a running memory span task. Two studies will attempt to determine the extent to which rehearsal strategies affect short-term memory and whether or not retarded persons exhibit rehearsal deficiencies. Finally, a study will be replicated on a longitudinal basis in order to evaluate the constancy of memory processes.